A Good Night's Sleep and a Good Memory Go Hand in Hand

by Melissa Gibbs, guest blogger

As exam time looms ahead at most modern day Universities, it is common for students to stay up all night cramming, convinced that a few more crucial hours of study can seal the deal in so far as remembering important information is concerned. A recent study by scientists at the Griffith Lab, however, has shown that the mechanism that promotes sleep also consolidates memory; in other words, it is our memory neurons that make us feel sleepy, since we need to sleep in order for our short-term memory to be converted into long-term memory. Previous to the study, scientists already knew that sleep deprivation resulted in problems remembering facts and events; however, they did not know whether the same mechanism that promoted sleep also consolidated memory, or whether two independent processes worked side-by-side.

Researchers, Paula Haynes, Leslie Griffith and Bethany Christmann focussed their research on dorsal paired medial neurons (DPM), which are known as memory consolidators in small fruit flies (Drosophila). They noted that when DPM neurons were activated, the flies slept for longer periods; when they were deactivated, the flies stayed awake.

The researchers noted that these memory consolidators, located in an area known as the 'mushroom body' (akin to the hippocampus, where our memory is stored), induces sleepiness so that short-term memories can become converted into long-term memories. Christmann notes, "It's almost as if that section of the mushroom body were saying 'Hey, stay awake and learn this'. Then, after a while, the DPM neurons start signaling to suppress that section, as if to say 'You're going to need sleep if you want to remember this later'."

Knowledge of the fact that sleep and memory processes are connected is highly significant, since it can help scientists learn more about how the human brain works. Christmann noted that their findings could aid scientists understand how sleep or memory is affected in those battle insomnia or memory disorders. The news will undoubtedly be welcome by the many individuals facing sleeping disorders on a daily basis; in Australia, between 13% and 33% of adults have difficulty either falling asleep or staying asleep, and sleep disturbances are currently the third most common psychological reason why a patient would seek help in general practice. Insomnia doubles the risk of attention and can also pose a major obstacles for those attempting to overcome addiction, since interference with the normal circadian rhythm can lead to everything from anxiety to aggression and depression.

In related news, a study published in August, 2015 by neuroscientist, Dr. Ravi Allada, and his team at Northwestern University, has also made great inroads into the nature of what keeps us awake or asleep; the study discovered how an animal's biological clock causes it to wake up in the morning and fall asleep at night. Apparently, it's all got to do with sodium and potassium levels; high sodium channel activity in brain circadian neurons turn specific cells 'on', thereby waking the animal, and high potassium channel activity at night turns these same cells 'off', affording the animal some much-needed rest. These processes were observed in both flies and mice, suggesting, notes Allada, that the underlying mechanism that determines when we sleep and wake up, is ancient and universal. Allada states: "This oscillation mechanism appears to be conserved across several hundred million years of evolution. And if it's in the mouse, it is likely in humans, too." The researchers referred to this process as a 'bicycle mechanism', in which two pedals (sodium and potassium currents, respectively), relay vital information regarding time to the neurons. They noted that it was highly significant that the same sleep-wake cycle mechanism could be observed in a fly and a more complex animal such as a mouse. Moreover, flies are diurnal and mice nocturnal yet their sleep-wake cycles are controlled in the exact same way. Their findings also showed that animals missing a sodium channel displayed poor circadian rhythms.

Scientists hope to use these findings to create new medication targeting sleep-wake related issues, such as those encountered by individuals working night shifts or facing jetlag. The idea is to reset the individual's internal clock to suit their particular situations or circumstances.